Abstract
The scope of the paper is limited to a discussion of simple turbocharging (i.e. precluding multi-stage compressors or turbines, inter-cooling, etc.) and considers only four-stroke engines. On the basis of published information the constant-pressure and pulse-exhaust systems are re-examined in the light of the requirements of an automotive engine. It is concluded that the pulse system is essential for use with existing transmissions.
Methods of assessing the thermodynamic performance of the compressor-turbine-manifold system, operating on the pulse principle, are reviewed and an overall coefficient defined. Existing methods of analysing the performance of exhaust turbines when operating in a non-steady flow field are discussed and the limitations noted. A slightly modified method, based on earlier work, is presented and should prove of value for direct application to an experimental turbocharged engine. A new method for determining the energy transmission efficiency of the exhaust manifold is derived and some preliminary results from a typical automotive engine are presented.
The overall performance of a simple turbocharged engine is examined by the use of an analogue computer model and the importance of the manifold and turbine efficiencies emphasized.
It is concluded that a complete solution of the torque-speed relationship problem is unlikely to be found using simple turbocharging alone, particularly with the 50 per cent reaction radial turbines at present in almost universal use. The analogue model of a turbocharged engine is likely to prove of increasing value and be a useful adjunct to experimental work.
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